LeetCode--Remove Duplicates from Sorted List II

描述

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers

from the original list.

For example,

Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode *deleteDuplicates(ListNode *head) {
ListNode *dummy = new ListNode(-1);
dummy->next = head;
if(head == NULL)
return head;

ListNode *prev = dummy;
ListNode *cur = head;
ListNode *next = NULL;
int dup = 0;
for(; cur!=NULL; )
{
next = cur->next;
if(next){
if(cur->val == next->val){
cur->next = next->next;
delete next;
dup = 1;
//next = cur->next;
}else{
if(dup == 1)
{
dup = 0;
prev->next = cur->next;
delete cur;
cur = prev->next;
}else{
prev = cur;
cur = prev->next;
}
}
}else
{
if(dup == 1)
{
dup = 0;
prev->next = cur->next;
delete cur;
cur = prev->next;
}else{
cur = cur->next;
prev = cur;
}
}
}

return dummy->next;
}
};墨迹半天解决了。确实不好想，有些边界需要注意。